In prior art display devices the common method of displaying measured characteristics, such as voltage, power, etc., is to provide electromechanical meters or fluid gages. In general, the electromechanical meters provide the required resolution but they can be easily misinterpreted and are relatively complex and bulky. For example, it is common to use a single meter movement for a variety of scales by incorporating shunt and series resistors and other components, along with switches and the like. The operator must then determine the position of the meter, note the particular scale at which the device is set and make minor calculations to determine the actual value of the measured characteristic. Thus, there is much room for errors in reading or in the minor calculations if the operator is under stress or in a hurry. Further, the electromechanical meters are generally relatively fragile and limited in their use.
In recent years some attempts have been made at displaying some measured characteristics in a visual format. One of the most common is a digital display, such as digital volt meters and the like wherein the measurement is converted directly to a digital reading. Again, these devices are relatively limited in their application.
Some work has also been done in utilizing bar graph presentations on cathode ray type displays. These presentations have generally been limited to hystogram type presentations. Some limited bar graph presentations have been utilized wherein most of the information is permanently displayed on the face of a cathode ray tube or the like and some form of line is generated to indicate the measured characteristic (i.e., amplitude). These devices have all of the limitations of electromechanical meters, since they are very limited in application.